This invention relates to brushless DC motors electronically commutated and more particularly to brushless DC fan motors that are of simple construction, inexpensive to manufacture, and reliable.
A typical goal in the manufacture of fans is a motor that is very simple and consequently has a low manufacturing cost. In AC motors for fans, the side armature AC motor comes closest to achieving these goals. However, recently, DC motors for fans have become more and more attractive, particularly for fans used to cool electronics where DC power is available.
Brushless DC motors using Hall effect devices to sense the commutation points as the rotor rotates are well known in the art. One or more stator coils are repeatedly energized or have their energization reversed to effect relocation of the electromagnetic field produced by poles of the stator core. A permanent magnet rotor is continuously attracted to the new electromagnetic pole locations. For commutation, one or more Hall effect devices senses the location of the poles of the rotor permanent magnet to control the energization of the stator winding or windings, or a Hall device detects the position of one or more commutation magnets mounted to rotate with the rotor and provided especially to indicate, by changing the state of the Hall device, the commutation points as the rotor turns.
Many brushless DC motors have been complex in both their structure and their commutation circuitry. Where simple, low cost and reliable fan motors have been needed these brushless DC motors, which might more appropriately have been used for, say, precise disc or tape drives, have been too expensive for the simple purpose of fan rotation.